INVESTMENTS IN MARKETING COOPERATIVES: (Details) (USD $)	12 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010
Investments in marketing cooperatives
Outstanding advances due to investee, current liability	$ 5,307,000	$ 4,831,000
Outstanding advances due to investee, long-term current liability	5,033,000
Outstanding advances to investee	34,619,000	32,184,000
Outstanding short-term debt with CoBank	110,640,000	66,197,000
United
Investments in marketing cooperatives
Ownership interest (as a percent)	62.00%
Voting interest (as a percent)	33.33%
Amount of losses exceeding the carrying amount of investment	5,900,000
Carrying amount of the investment	0
Outstanding advances due to investee, current liability	873,000
Outstanding advances due to investee, long-term current liability	5,000,000
Outstanding advances to investee	34,100,000	30,500,000
Amount reimbursed for services provided	1,000,000	1,000,000	1,000,000
Midwest
Investments in marketing cooperatives
Ownership interest (as a percent)	55.00%
Voting interest (as a percent)	25.00%
Carrying amount of the investment	82,000
Outstanding advances due to investee, current liability	4,400,000	4,800,000
Amount reimbursed for services provided	152,000	129,000	122,000
Outstanding short-term debt with CoBank	6,100,000
Short-term debt of investee with CoBank, ACB, guaranteed amount	$ 3,200,000